Modern semiconductor processing systems include cluster tools that integrate a number of process chambers together in order to perform several sequential processing steps without removing the substrate from the highly controlled processing environment. These chambers may include, for example, degas chambers, substrate pre-conditioning chambers, cooldown chambers, transfer chambers, chemical vapor deposition chambers, physical vapor deposition chambers, and etch chambers. The combination of chambers in a cluster tool, as well as the operating conditions and parameters under which those chambers are run, are selected to fabricate specific structures using a specific process recipe and process flow.
Once the cluster tool has been set up with a desired set of chambers and auxiliary equipment for performing certain process steps, the cluster tool will typically process a large number of substrates by continuously passing them, one by one, through a series of chambers or process steps. The process recipes and sequences will typically be programmed into a microprocessor controller that will direct, control and monitor the processing of each substrate through the cluster tool. Once an entire cassette of wafers has been successfully processed through the cluster tool, the cassette may be passed to yet another cluster tool or stand alone tool, such as a chemical mechanical polisher, for further processing.
One example of a fabrication system of the type described above is the cluster tool disclosed in U.S. Pat. No. 6,222,337 (Kroeker et al.), and reproduced in FIGS. 1 and 2 herein. The magnetically coupled robot disclosed therein is equipped with robotic arms having a frog-leg type construction that are adapted to provide both radial and rotational movement of the robot blade within a fixed plane. The radial and rotational movements can be coordinated or combined to allow for pickup, transfer and deliver of substrates from one location within the cluster tool to another location. For example, the robotic arm may be used to move substrates from one processing chamber to an adjacent chamber.
FIG. 1 is a schematic diagram of the integrated cluster tool 10 of Kroeker et al. Substrates are introduced into, and withdrawn from, the cluster tool 10 through a cassette loadlock 12. A robot 14 having a blade 17 is located within the cluster tool 10 to transfer the substrates from one process chamber to another. These process chambers include cassette loadlock 12, degas wafer orientation chamber 20, preclean chamber 24, PVD TiN chamber 22 and cooldown chamber 26. The robot blade 17 is illustrated in the retracted position in which it can rotate freely within the chamber 18.
A second robot 28 is located in transfer chamber 30 and is adapted to transfer substrates between various chambers, such as the cooldown chamber 26, preclean chamber 24, CVD Al chamber (not shown) and a PVD AlCu processing chamber (not shown). The specific configuration of chambers illustrated in FIG. 1 is designed to provide an integrated processing system capable of both CVD and PVD processes in a single cluster tool. A microprocessor controller 29 is provided to control the fabricating process sequence, conditions within the cluster tool, and the operation of the robots 14, 28.
FIG. 2 is a schematic view of the magnetically coupled robot of FIG. 1 shown in both the retracted and extended positions. The robot 14 (see FIG. 1) includes a first strut 81 rigidly attached to a first magnet clamp 80 and a second strut 82 rigidly attached to a second magnet clamp 80′. A third strut 83 is attached by a pivot 84 to strut 81 and by a pivot 85 to a wafer blade 86. A fourth strut 87 is attached by a pivot 88 to strut 82 and by a pivot 89 to wafer blade 86. The structure of struts 81-83, 87 and pivots 84, 85, 88, and 89 form a “frog leg” type connection of wafer blade 86 to magnet clamps 80,80′.
When magnet clamps 80,80′ rotate in the same direction with the same angular velocity, then the robot also rotates about axis x in this same direction with the same velocity. When magnet clamps 80, 80′ rotate in opposite directions with the same absolute angular velocity, then there is no rotation of assembly 14, but instead there is linear radial movement of wafer blade 86 to a position illustrated by dashed elements 81′-89′.
A wafer 35 is shown being loaded on wafer blade 86 to illustrate that the wafer blade can be extended through a wafer transfer slot 810 in a wall 811 of a chamber 32 to transfer such a wafer into or out of the chamber 32. The mode in which both magnet clamps 80, 80′ rotate in the same direction at the same speed can be used to rotate the robot from a position suitable for wafer exchange with one of the adjacent chambers 12, 20, 22, 24, 26 (see FIG. 1) to a position suitable for wafer exchange with another of these chambers. The mode in which both magnet clamps 80, 80′ rotate with the same speed in opposite directions is then used to extend the wafer blade into one of these chambers and then extract it from that chamber. Some other combination of clamp rotation can be used to extend or retract the wafer blade as the robot is being rotated about axis x.
To keep wafer blade 86 directed radially away from the rotation axes x, an interlocking mechanism is used between the pivots or cams 85, 89 to assure an equal and opposite angular rotation of each pivot. The interlocking mechanism may take on many designs. One possible interlocking mechanism is a pair of intermeshed gears 92 and 93 formed on the pivots 85 and 89. These gears are loosely meshed to minimize particulate generation by these gears. To eliminate play between these two gears because of this loose mesh, a weak spring 94 (see FIG. 4) may be extended between a point 95 on one gear to a point 96 on the other gear such that the spring tension lightly rotates these two gears in opposite directions until light contact between these gears is produced.
Although robots of the type depicted in U.S. Pat. No. 6,222,337 (Kroeker et al.) have many desirable features, robots of this type also have some shortcomings. In particular, it has been found that robots of this type often exhibit excessive wear in the wrist 85′, 89′ and elbow 84′, 88′ joints. This problem results in excessive maintenance requirements and interruptions to the manufacturing process. There is thus a need in the art for a robotic assembly which requires less maintenance and exhibits less wear in these areas. These and other needs are met by the devices and methodologies disclosed herein and hereinafter described.